Buffered substrate for semiconductor devices

Abstract

The invention provides a buffered substrate that includes a substrate, a buffer layer and a silicon layer. The buffer layer is disposed between the substrate and the silicon layer. The buffer layer has a melting point higher than a melting point of the substrate. A polycrystalline silicon layer is formed by crystallizing the silicon layer using a laser beam.

What is claimed is: 
     
       1. A buffered substrate formed by using a laser beam, comprising: a substrate including at least one of silicon dioxide, glass, quartz and metal;   a buffer layer formed over the substrate, the buffer layer having a melting point higher than a threshold temperature of the substrate; and   a silicon layer formed over the buffer layer, wherein the silicon layer is crystallized using a laser beam after being formed over the buffer layer, the buffer layer including uniform silicon crystal grains having a grain size variation of less than or equal to a factor of about 2, and determining a nucleation density of the silicon layer.   
     
     
       2. The buffered substrate of claim 1, wherein the buffer layer forms islands over the substrate. 
     
     
       3. The buffered substrate of claim 1, wherein the buffer layer comprises at least one of MgO, MgAl 2  O 4 , Al 2  O 3  and ZrO 2 . 
     
     
       4. The buffered substrate of claim 1, wherein the laser beam is one of an excimer laser beam and a YAG laser beam. 
     
     
       5. The buffered substrate of claim 1, wherein the silicon layer is an amorphous silicon layer before the silicon layer is crystallized. 
     
     
       6. The buffered substrate of claim 5, wherein a thickness of the amorphous silicon layer is less than or equal to about 100 nm. 
     
     
       7. The buffered substrate of claim 6, wherein a laser fluence range is between about 300 to 600 mJ/cm 2 . 
     
     
       8. The buffered substrate of claim 5, wherein the amorphous silicon layer is crystallized to form a polycrystalline silicon layer. 
     
     
       9. The buffered substrate of claim 8, wherein an average grain size of the polycrystalline silicon layer is less than about a thickness of the polycrystalline silicon layer. 
     
     
       10. The buffered substrate of claim 8, wherein a root-mean-square roughness of the polycrystalline silicon layer is less than or equal to about 6 nm. 
     
     
       11. A method for forming a buffered substrate using a laser beam, comprising: forming a buffer layer over a substrate, the substrate including at least one of silicon dioxide, glass, quartz and metal, the buffer layer having a melting point higher than a threshold temperature of the substrate;   forming a silicon layer over the buffer layer; and then   crystallizing the silicon layer using a laser beam, wherein the buffer layer includes uniform silicon crystal grains having a grain size variation of less than or equal to a factor of about 2, and determines a nucleation density of the silicon layer.   
     
     
       12. The method of claim 11, wherein the buffer layer forms islands over the substrate. 
     
     
       13. The method of claim 11, wherein the buffer layer comprises at least one of MgO, MgAl 2  O 4 , Al 2  O 3  and ZrO 2 . 
     
     
       14. The method of claim 11, wherein the silicon layer is an amorphous layer before the silicon layer is crystallized. 
     
     
       15. The method of claim 14, wherein a thickness of the amorphous silicon layer is less than or equal to about 100 nm. 
     
     
       16. The method of claim 14, further comprising crystallizing the amorphous silicon layer to form a polycrystalline silicon layer. 
     
     
       17. The method of claim 16, wherein an average grain size of the polycrystalline silicon layer is less than about a thickness of the polycrystalline silicon layer. 
     
     
       18. The method of claim 16, wherein a root-mean-square roughness of the polycrystalline silicon layer is less than or equal to about 6 nm.